Internal blow out preventer

ABSTRACT

An internal blow out preventer for use in a drill string, comprising a housing having an outer valve closure element and where the outer valve closure element is configured to be moved between an open and a closed position, wherein the outer valve closure element is provided with an inner valve closure element that is configured to be moved between an open and a closed position inside the outer valve closure element.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/521,564 filed Aug. 27, 2012, now U.S. Pat. No. 8,950,430, entitled“Internal Blow Out Preventer,” which is a 35 U.S.C. §371 national stageapplication of PCT/NO2011/000010 filed Jan. 10, 2011, which claims thebenefit of Norwegian Application No. 20100037 filed Jan. 11, 2010, allof which are incorporated herein by reference in their entireties forall purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

1. Field of the Disclosure

There is presented an internal blow out preventer. More precisely thereis presented an internal blow out preventer for use in a drill string,comprising a housing with a valve closure element and associated seals,wherein the valve closure element is configured to be moved between anopen and a closed position.

2. Background of the Technology

The primary function of an Internal Blow Out Preventer (IBOP) is to shutoff the mud (drilling fluid) passage on the inside of a drill string inthe event well pressure exceeds limits during drilling operations on adrill rig.

However, the IBOP is also frequently used to prevent spillage ofdrilling fluids during each instance the top drive of the drill rig isdisconnected from the drill string, e.g. each instance a new pipe orsection of pipes is added to the drill string. This secondary functionof the IBOP as a “mud saver” results in increased wear of the seals ofthe valve that has several un-desirable consequences.

One disadvantage is reduced service life of the IBOP valve, leakage whenthe valve is being used as mud saver after pressure testing, risk of rigdowntime earlier than predicted, and more frequent need for sealreplacements.

Although the use of two individual valves would solve the aboveproblems, that solution would require additional space in the drill stemof the top drive (drilling machine), space which is not alwaysavailable. The length of the drill stem located between the top driveand drill string, is limited by the travel of the top drive pipehandler, which needs to be able to grip around the box of the uppermostpipe of the drill string, just below the drill stem.

A normal set up of the drill stem between the top drive and drill stringincludes a cross-over sub, a remotely operated IBOP, and a second IBOP,the second IOBP being used as a closing valve at the upper end of thedrill string remaining in the well and disconnected from the top drive,and a saver sub that takes the wear and damage of threads when the topdrive and the drill string are connected or disconnected.

The IBOP is normally a ball valve, with the advantage that sealing has aradial symmetry, making it relatively easy to manufacture.

This disclosure relates to apparatuses intended to address at least someof the disadvantages of the prior art.

BRIEF SUMMARY OF THE DISCLOSURE

There is presented an internal blow out preventer for use in a drillstring, the internal blow out preventer comprising a housing with avalve closure element and associated seals and where the valve closureelement is configured to be moved between an open and a closed position,wherein the valve closure element is provided with an inner valveclosure element that is configured to be moved between an open and aclosed position inside the outer valve closure element.

A valve body is provided with an additional inner valve closure elementwhich is operated independently of the outer valve closure elementenabling the mud saving operation without compromising the sealingperformance of the IBOP and without the need for additional length ofthe drill stem, i.e. between the top drive and drill string.

The flow area of the inner valve closure element may be comparable to,substantially equal to or equal to the flow through area of the outervalve closure element. Thus the inner valve closure element will notrestrict flow through the IBOP when fully open.

The outer valve closure element may be separable, and a junction betweena first part and a second part may be positioned so as to be out ofcontact with the seals during movement between the open and the closedposition. This feature is intended to decrease wear of the seals thatmight otherwise occur.

The inner valve closure element may have a spherical or cylindricalform. Shaped as a ball, the inner valve closure element maintainscertain benefits of using flat, circular seas. However, it may be morechallenging mechanically to fit a ball rather than a cylinder insideanother ball. Shaped as a cylinder, the inner valve closure elementrequires more complex machining to accommodate seals but eases themachining of the inner valve closure element and improves the structuralintegrity of the outer valve closure element. It is worth mentioningthat small leaks during mud saving operations are generally acceptableand may permit less stringent machining tolerances.

The outer and inner valve closure elements may be rotatable about acommon axis of rotation.

Certain embodiments of the valve described herein are intended toaddress problems of reduced service life for the IBOP seals as the valveclosure element remains stationary while the inner valve closure elementis closed for the mud saving operation.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of an embodiment of an IBOP is explained with reference tothe enclosed drawings, where:

FIG. 1 shows a cross section of an internal blow out preventer, IBOP,according to the disclosure herein;

FIG. 2 shows a larger scale cross section of IBOP parts when used as amud saver;

FIG. 3 shows the IBOP in an exploded view;

FIG. 4 shows a cross section of the IBOP in an initial stage of closingas a blow out preventer; and

FIG. 5 shows the same as in FIG. 4 in the completely closed position.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

On the drawings the reference number 1 denotes an internal blow outpreventer comprising a housing 2, a spherical outer valve closureelement 4 and a spherical inner valve closure element 6.

The housing 2 in this embodiment is provided with internal threads 8 atits upper end portion 10 and external threads 12 at its lower endportion 14 in order to connect to a pin/box configuration of a not shownTop Drive drill stem.

‘Upper’ and ‘lower’ here refers to the IBOP in its normal workingposition as shown on the drawings.

A central, longitudinal bore 16 extends between the two end portions 10,14. The bore 16 corresponds with a bore of the not shown drill string.

A shoulder 18 is formed in the bore 16 as an upper portion 20 of thebore 16 has a larger diameter than the rest of the bore 16.

The outer valve closure element 4 is positioned in the upper portion 20of the bore 16 and connected to two hollow shafts 22 that are protrudingthrough shaft openings 24 in the housing 4. The outer valve closureelement 4 and the hollow shafts 22 are rotatable about axis 26. One ofthe hollow shafts 22 is connected to a not shown first actuator.

A lower ring 28 that abuts the shoulder 18, is provided with a firstsealing surface 30 that is configured to seal against the outer valveclosure element 4. A lower ring seal 32 provided in the lower ring 28prevents fluid flow between the lower ring 28 and the body 2.

An upper ring 34, placed above the outer valve closure element 4, isprovided with a second sealing surface 36 that is configured to sealagainst the outer valve closure element 4. An outer ring seal 38provided in the upper ring 34 prevents fluid flow between the upper ring34 and the body 2.

The first sealing surface 30 and the second sealing surface 36constitute the outer valve sealing surfaces.

The outer valve closure element 4 has an opening 40, with an areacomparable, substantially equivalent to or equal to the cross sectionarea of the lower portion of bore 16.

The inner valve closure element 6 is positioned inside the outer valveclosure element 4 and connected to two shafts 42. Each of the shafts 42extend through a concentric bore 44 in the respective hollow shafts 22.The inner valve closure element 6 and the shafts 42 are rotatable aboutaxis 26.

A not shown second actuator is connected to one of the shafts 42.

Seals 46 prevent fluid from flowing between the hollow shafts 22 and thehousing 2 and between the hollow shafts 22 and the shafts 42.

Inner valve seals 48 positioned in corresponding recesses 50 inside theouter valve closure element 4 prevent fluid from passing between theouter valve closure element 4 and the inner valve closure element 6.

The inner valve closure element 6 has an opening 52 of comparable,substantially equal or equal cross section area to that of the opening40 of the outer valve closure element 4.

In an embodiment as shown in FIG. 2, the outer valve closure element 4is made of a first valve segment 54 and a second valve segment 56.

After the inner valve seals 48 and the inner valve closure element 6 arepositioned inside the outer valve closure element 4, the first andsecond valve segments 54, 56 are joined at an interface 58 using bolts60.

In FIGS. 3 to 5 the housing 2 is removed in order to better show theoperating functions of the IBOP 1.

When used as a mud saver, the inner valve closure element 6 of the IBOP1 is rotated about axis 26 to close the valve opening 40 thus preventingmud from flowing through the IBOP 1, see FIG. 2.

The outer valve closure element 4 is not turned, and no wear is causedon the first and second sealing surfaces 30 and 36.

When used as an IBOP, the inner valve closure element 6 is placed in theopen position, see FIGS. 4 and 5. The inner valve body seals 48 are thusnot utilised for IBOP mode of operation.

The outer valve closure element 4 is rotated about axis 26 to a closedposition, see FIG. 5, preventing flow through the IBOP 1. The first andsecond sealing surfaces 30 and 36, not subject to wear from mud saveruse, function as a reliable, leak-proof barrier against the wellpressure.

The interface 58 does not pass over the sealing surfaces 30, 36 duringclosing or opening of the outer valve closure element 4.

The invention claimed is:
 1. An internal blow out preventer comprising:a housing having a central axis and a bore extending axiallytherethrough; a spherical outer valve closure element rotatably disposedin the housing, wherein the outer valve closure element is configured tomove between an open position and a closed position; and a sphericalinner valve closure element rotatably disposed within the outer valveclosure element, wherein the inner valve closure element is configuredto move between an open position and a closed position within the outervalve closure element; wherein the outer valve closure element comprisesa pair of radially extending shafts rotatably coupled to the housing. 2.The internal blow out preventer of claim 1, further comprising a firstring coaxially disposed in the housing axially adjacent the outer valveclosure element, wherein the first ring includes an annular sealingsurface that slidingly engages the outer valve closure element and isconfigured to seal against the outer valve closure element.
 3. Theinternal blow out preventer of claim 2, further comprising a second ringcoaxially disposed in the housing axially adjacent the outer valveclosure element, wherein the second ring includes an annular sealingsurface that slidingly engages the outer valve closure member and isconfigured to seal against the outer valve closure element.
 4. Theinternal blow out preventer of claim 1, wherein the outer valve closureelement comprises a bore extending therethrough, and wherein the outervalve closure element is configured to rotate about an axis of rotationbetween the open position and the closed position; wherein the innervalve member comprises a bore extending therethrough, and wherein theouter valve closure element is configured to rotate about the axis ofrotation between the open position and the closed position.
 5. Theinternal blow out preventer of claim 1, wherein a flow area of a valveopening of the inner valve closure element is substantially the samesize as a flow area of a valve opening of the outer valve closureelement.
 6. The internal blow out preventer of claim 1, wherein theouter valve closure element comprises: an annular recess extending intoan inner surface of the outer valve closure element; and an annular sealdisposed within the annular recess, wherein the annular seal isconfigured to slidingly engage and seal against the inner valve closureelement.
 7. The internal blow out preventer of claim 1, wherein theinner valve closure element comprises a pair of radially extendingshafts rotatably coupled to the housing and disposed within the radiallyextending shafts of the outer valve closure element.
 8. The internalblow out preventer of claim 1, wherein the internal blow out preventerhas an open configuration with the inner valve closure element in theopen position and the outer valve closure element in the open position;wherein in the open configuration the internal blow out preventer isconfigured to allow for the flowing of a fluid between a first end ofthe housing and a second end of the housing.
 9. The internal blow outpreventer of claim 8, wherein the internal blow out preventer has a mudsaver configuration with the inner valve closure element in the closedposition and the outer valve closure element in the open position;wherein in the mud saver configuration the internal blow out preventeris configured to prevent the flowing of a fluid between a first end ofthe housing and a second end of the housing.
 10. The internal blow outpreventer of claim 8, wherein the internal blow out preventer has a blowout preventer configuration with the inner valve closure element in theopen position and the outer valve closure element in the closedposition; wherein in the blow out preventer configuration the internalblow out preventer is configured to prevent the flowing of a fluidbetween a first end of the housing and a second end of the housing. 11.An internal blow out preventer comprising: a housing having a first end,a second end and a central bore extending between the first end and thesecond end along a longitudinal axis of the housing; an outer valvemember rotatably disposed within the housing, wherein the outer valveelement has a bore extending therethrough and an axis of rotation; andan inner valve member rotatably disposed within the outer valve member,wherein the inner valve member has a bore extending therethrough and anaxis of rotation coaxially aligned with the axis of rotation of theouter valve member; wherein the inner valve member has a spherical outersurface that slidingly engages an inner surface of the outer valvemember; wherein the outer valve member comprises a pair of radiallyextending shafts rotatably coupled to the housing.
 12. The internal blowout preventer of claim 11, further comprising a first ring coaxiallydisposed in the housing axially adjacent the outer valve member, whereinthe first ring includes a first annular sealing surface that slidinglyengages the outer valve closure member and is configured to seal againstthe outer valve member.
 13. The internal blow out preventer of claim 12,further comprising a second ring coaxially disposed in the housingaxially adjacent the outer valve member, wherein the second ringincludes a second annular sealing surface that slidingly engages theouter valve closure member and is configured to seal against the outervalve member.
 14. The internal blow out preventer of claim 11, whereinthe first annular sealing surface of the first ring slidingly engages aspherical outer surface of the outer valve member.
 15. The internal blowout preventer of claim 11, wherein the outer valve member comprises: anannular recess extending into an inner surface of the outer valvemember; and an annular seal disposed within the annular recess, whereinthe annular seal is configured to slidingly engage and seal against thespherical outer surface of the inner valve member.
 16. The internal blowout preventer of claim 11, wherein the inner valve member comprises apair of radially extending shafts rotatably coupled to the housing anddisposed within the radially extending shafts of the outer valve member.17. The internal blow out preventer of claim 11, wherein the internalblow out preventer has an open configuration with the inner valve memberin the open position and the outer valve member in the open position;wherein in the open configuration the internal blow out preventer isconfigured to allow for the flowing of a fluid through the central boreof the housing.
 18. The internal blow out preventer of claim 17, whereinthe internal blow out preventer has a mud saver configuration with theinner valve member in the closed position and the outer valve member inthe open position; wherein the internal blow out preventer has a blowout preventer configuration with the inner valve member in the openposition and the outer valve member in the closed position; wherein inthe mud save configuration and the blow out preventer configuration theinternal blow out preventer is configured to prevent the flowing of afluid through the central bore of the housing.